As cellular wireless systems evolve from 2G to 4G, there is increasing demand for radio frequency (RF) chipsets to support larger numbers of bands. Providing the chipsets with the ability to handle these additional bands may require adding additional transceivers, filters, power amplifiers, passive components and switches to the chipset front end, and this increases the cost and complexity of the chipsets. The RF system of a cellphone mainly consists of two parts: the transceiver, which is often a single complementary metal oxide semiconductor (CMOS) chip, and the RF front-end (including various on-board components: filters, duplexers, RF switches, power amplifiers and passives). While the CMOS transceiver can be designed to be shared by different bands or modes, generally called a multi-mode/multi-band transceiver design, the front-end part, especially the filters and duplexers, cannot be shared between different bands, simply because they operate in different frequency range. The presence of these additional elements to support more bands/modes may cause the front end to become a limiting factor when attempting to increase performance and reduce size and cost.
Conventional multi-band and/or multi-mode RF chipset front ends may include devices such as RF switches, power amplifiers, acoustic filters and passives, e.g., inductors and capacitors. While the CMOS chip elements generally may scale continuously, resulting in lower cost and smaller size with new technological advances, the front end does not always scale as readily. One approach to this situation has been to integrate multiple chips, e.g., GaAs antenna switches, GaAs power amplifiers, CMOS controllers, surface acoustic wave (SAW) filters, integrated passive devices, etc. onto a single laminate or ceramic substrate. This approach may be referred to as a “system-in-package” solution for front-end integration. There is also interest in addressing the multi-band complexity problem at a system architecture level by introducing a tunable front end. To realize a low-loss multi-band tunable system, a way must be found to implement high-Q tunable passives, such as semiconductor varactors and MEMS-based tunable capacitors, and high-performance RF switches into a single arrangement. Front end integration may also be useful for reducing the overall size and cost of multiband and/or multi-mode RF transceiver chipsets. It would therefore be desirable to provide a chipset that integrates CMOS components with other front end components in a space- and cost-effective manner.